From 8757e0aa115e4e5fe484f8e89589cb81d71e0518 Mon Sep 17 00:00:00 2001
From: hrkrshnn <git@hrkrshnn.com>
Date: Sun, 9 Apr 2023 15:42:53 +0200
Subject: [PATCH] feat: add support for `push0` in libevmasm

See https://eips.ethereum.org/EIPS/eip-3855

Note: `push0` costs 2 gas, i.e., `Tier::Base` unlike other pushes.
---
 libevmasm/Instruction.cpp | 2 ++
 libevmasm/Instruction.h   | 9 +++++----
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/libevmasm/Instruction.cpp b/libevmasm/Instruction.cpp
index 418a6e185..2c313fd75 100644
--- a/libevmasm/Instruction.cpp
+++ b/libevmasm/Instruction.cpp
@@ -94,6 +94,7 @@ std::map<std::string, Instruction> const solidity::evmasm::c_instructions =
 	{ "MSIZE", Instruction::MSIZE },
 	{ "GAS", Instruction::GAS },
 	{ "JUMPDEST", Instruction::JUMPDEST },
+	{ "PUSH0", Instruction::PUSH0 },
 	{ "PUSH1", Instruction::PUSH1 },
 	{ "PUSH2", Instruction::PUSH2 },
 	{ "PUSH3", Instruction::PUSH3 },
@@ -242,6 +243,7 @@ static std::map<Instruction, InstructionInfo> const c_instructionInfo =
 	{ Instruction::MSIZE,		{ "MSIZE",			0, 0, 1, false, Tier::Base } },
 	{ Instruction::GAS,			{ "GAS",			0, 0, 1, false, Tier::Base } },
 	{ Instruction::JUMPDEST,	{ "JUMPDEST",		0, 0, 0, true, Tier::Special } },
+	{ Instruction::PUSH0,		{ "PUSH0",			0, 0, 1, false, Tier::Base } },
 	{ Instruction::PUSH1,		{ "PUSH1",			1, 0, 1, false, Tier::VeryLow } },
 	{ Instruction::PUSH2,		{ "PUSH2",			2, 0, 1, false, Tier::VeryLow } },
 	{ Instruction::PUSH3,		{ "PUSH3",			3, 0, 1, false, Tier::VeryLow } },
diff --git a/libevmasm/Instruction.h b/libevmasm/Instruction.h
index 48ee37b5c..2fddb11d8 100644
--- a/libevmasm/Instruction.h
+++ b/libevmasm/Instruction.h
@@ -103,6 +103,7 @@ enum class Instruction: uint8_t
 	GAS,				///< get the amount of available gas
 	JUMPDEST,			///< set a potential jump destination
 
+	PUSH0 = 0x5f,       ///< place the value 0 on stack
 	PUSH1 = 0x60,		///< place 1 byte item on stack
 	PUSH2,				///< place 2 byte item on stack
 	PUSH3,				///< place 3 byte item on stack
@@ -207,7 +208,7 @@ constexpr bool isCallInstruction(Instruction _inst) noexcept
 /// @returns true if the instruction is a PUSH
 inline bool isPushInstruction(Instruction _inst)
 {
-	return Instruction::PUSH1 <= _inst && _inst <= Instruction::PUSH32;
+	return Instruction::PUSH0 <= _inst && _inst <= Instruction::PUSH32;
 }
 
 /// @returns true if the instruction is a DUP
@@ -231,7 +232,7 @@ inline bool isLogInstruction(Instruction _inst)
 /// @returns the number of PUSH Instruction _inst
 inline unsigned getPushNumber(Instruction _inst)
 {
-	return static_cast<uint8_t>(_inst) - unsigned(Instruction::PUSH1) + 1;
+	return static_cast<uint8_t>(_inst) - unsigned(Instruction::PUSH0);
 }
 
 /// @returns the number of DUP Instruction _inst
@@ -255,8 +256,8 @@ inline unsigned getLogNumber(Instruction _inst)
 /// @returns the PUSH<_number> instruction
 inline Instruction pushInstruction(unsigned _number)
 {
-	assertThrow(1 <= _number && _number <= 32, InvalidOpcode, std::string("Invalid PUSH instruction requested (") + std::to_string(_number) + ").");
-	return Instruction(unsigned(Instruction::PUSH1) + _number - 1);
+	assertThrow(_number <= 32, InvalidOpcode, std::string("Invalid PUSH instruction requested (") + std::to_string(_number) + ").");
+	return Instruction(unsigned(Instruction::PUSH0) + _number);
 }
 
 /// @returns the DUP<_number> instruction